Sources claim that a Hollywood director Sam Mendez, who won an Oscar for “American Beauty,” landed a deal with Cupertino, California-based Apple to film an alleged iPhone HD commercial that will help sell video calling to couch potatoes. Mendez, 44, is apparently auditioning several actors for the commercial who bragged about it on Twitter.

The same source also tipped Engadget’s editor Joshua Topolsky that Apple is internally referring to the iPhone HD as “Mammoth/N90.” Topolsky described how the commercial will highlight video calling as possibly the killer feature of the forthcoming fourth-generation iPhone:

A trusted source has confirmed to us that the ads will feature at least one spot where a mother and daughter are having a video chat conversation using the new front-facing camera that’s been spied on the face of that iPhone floating around Vietnam and Northern California.

Apple will most likely air several adverts to highlight different capabilities of the handset. The Californian firm has reportedly signed on pop sensation Lady GaGa to endorse the handset and appear in the inaugural commercial.

Apple is expected to launch the handset on Monday, June 7, when its chief executive Steve Jobs is scheduled to climb the stage at the San Francisco’s Moscone West at 10am and kickstart the annual developer conference with his trademark keynote. Meanwhile, Walmart just slashed the 16GB iPhone 3GS to $97 this morning (previously $199).

Boy Genius Report discovered that Apple stopped iPhone 3G shipments to its retailers, fueling the rumors that they’ll slide the iPhone 3GS to $99 while debuting the iPhone HD at the current $199/$299 price points with an obligatory two-year contract. One of the rumors also has it that the iPhone HD will feature 640×960 pixel resolution and an e-reading display for comfortably enjoying e-books purchased using an iBookstore client on the device.